Table of contents

The authors describe techniques which allow the study in undergraduate laboratories of the spectrum of atomic hydrogen. The Rydberg constant, the electron-proton mass ratio, and the fine-structure constant are evaluated from the measurements. The key to the series of experiments is a discharge tube in which atomic lines dominate over the molecular lines.

An apparatus to enable the observation of the Josephson effect is described. Simplifications in the construction make it suitable for use as an undergraduate laboratory experiment. The superconducting tunnel junction is formed after cooling to liquid helium temperature in an ordinary storage dewar. The conductors of a coaxial waveguide serve to draw together the two elements of the junction, which is then irradiated with X-band microwaves transmitted by the guide. Accurate determination of the microwave frequency and the voltage interval between the current steps lead to a value of e/h.

A system has been developed to allow the easy use of every digital integrated circuit in experiments proposed to students at various levels and on various courses. This system can be used from the simplest assembly to more sophisticated models for a relatively low cost. Furthermore, it can easily be developed according to future necessities of teaching and to the appearance of new components.

In University teaching computers have mainly been used in computer assisted instruction projects. The author presents further methods for applying computers in science education. The author's approach was to combine the teaching aims of a particular subject-e.g. physics-with aspects of computing relevant to a given application. The author developed a special course as well as two laboratories and now reports on methods and practical experiences.

The Nukiyama and Leidenfrost temperatures of the range of n-alkanes from pentane to hexadecane have been investigated, and their relationships to the standard boiling points determined. The Nukiyama temperatures prove to be only some 40 degrees C above the latter, showing that maximum evaporation rates are produced by contact with surfaces not nearly so hot as might intuitively be expected. A temperature increase of only some 20-30 degrees C beyond this point is sufficient to put the hydrocarbon into the slowly-evaporating Leidenfrost regime.

Reference to the solution of the Schrodinger equation does not give much physical insight into the problem of stability because it is far from obvious how the conclusion follows from the equation. The common arguments derived from the Heisenberg uncertainty principle are not sufficient to establish the existence of a stable ground state. The proof for a lower bound of the hydrogen hamiltonian may be recast into physical terms by introducing an effective localisation potential.

Interfacial phenomena play such a crucial role in life processes that the teaching of them must be an essential part of undergraduate programmes in life sciences. However, the role of interfacial tension, seen as a force per unit length of the separation perimeter between different media, is not always clearly seen in this teaching. The authors illustrate the difficulties by considering several problems of radial symmetry, in particular that of a liquid drop laid down on a solid plane or on top of an immiscible liquid, the role of gravity being taken into account. In addition to the boundary condition at the rim of the drop (the classical Young's relation), the balance between the Laplace and the hydrostatic force over the surfaces can be expressed as a condition at the perimeter which should not be confused with the previous condition. The confusion is the cause of unsatisfactory derivations of relations such as capillary ascent in a tube (Jurin's formula).

A model simulating the operation of the human eye has been constructed for use in a practical medical physics course. The following experiments carried out with the aid of this model are described: (i) Refractive power measurements to determine whether the eye is myopic or hypermetropic, calculation of the refractive power of the lens needed to correct this condition if present and testing of the lens prescribed in this way. (ii) Accommodation measurements. (iii) Simulation of the surgical removal of the crystalline lens of the eye which is often necessary in the treatment of cataract, and calculation of: (a) the power of the lens to be implanted in the eye to correct this aphakia, or (b) the power of the lens needed to correct the aphakia if no lens is implanted; and testing of the prescribed lenses. (iv) Demonstration of the effect of pupil diameter on depth of focus. (v) Demonstration of the influence of ocular opacity-caused e.g. by cataract-on the sharpness of the image on the retina.

Statements with implicit meanings are often used in physics. The paper deals with the importance and the possible consequences of such a practice, in the specific realm of constants. The question in fact is what meanings are triggered by common statements containing the word 'constant' and the ensuing difficulties which result. The word 'constant' may evoke a range of meanings with the two following notions at each end: number, the essential being its numerical value; and a constant function of certain variables, the important thing now being the listing of these variables. In this way constants appear as a particular aspect of functions of several variables. The results of an investigation among French and Belgian students at the beginning of their studies at University are reported and analysed. The usual interpretation of the word 'constant' is biased towards the numerical aspect of this notion, at the expense of its functional meaning. Lastly a plea follows for using exercises of 'text criticism' as pedagogical tools in teaching.

The equation of state for solids was published by Gruneisen in 1926; however it had a long and chequered history before that. A closely similar equation was first written down as early as 1843 on theoretical grounds-where it must be understood that the theories were those prevailing at the time and the mathematical methods were those then acceptable among physicists. The basis was the plausible idea that forces produced by heat (or caloric) were identical with mechanical forces, so that in all metals the thermal expansion coefficient should be proportional to Young's modulus. When the problem was tackled again in the present century, the theoretical model assumed that the law of force between atoms in metals was universal. Only when Gruneisen came to write his third paper was the equation fully understood.

A third-year undergraduate's essay written as part of the final honours examinations in science at Cambridge University is presented. It describes the history of the use of combustion by the human race, from the discovery of fire to the development of fusion power. This brief survey is presented in the form of a field report from an extraterrestrial being from Capella II written for the Journal of Applied Psychology of that planet.